Generally flat thin cross-section piece-parts of steel or rigid laminates of steel and another metal or rigid plastic material frequently might be fabricated by being stamped from a blank of material between matched tool components of a stamping press. A conventional stamping press will have separate sequential punch stations each with a pair of matched punch and die tool components, and the blank of material will be advanced through the stations where sequential strikes against it might be made by moving the tool components toward and away from one another, along axes generally normal to the blank material therebetween. This stamping procedure allows the use of matched tool components that can be economically made, and that will experience long service lives and be capable of reshaping under standard techniques and with conventional tolerances.
Efforts are also taken to make sure that the blank material is flat or planar in the stamping press, so that the piece-part will be flat and planar after being stamped. This can be more fully appreciated in the instance when the blank material is in the form of a continuous web unwound as needed from a coiled reel, whereby the web blank even when unwound might actually have slight three-dimensional curvatures (or biases to curve). In such instances, straightening or leveling equipment might be used to reshape the web to be flat and planar upon entering the press, in an effort to eliminate a curvature or bias in the stamped piece-part.
However, stamping specifications might call for the finished piece-part to have a slight three-dimensional bow. Prior to this invention, efforts to stamp slightly bowed piece-parts directly from a flat blank in a single or sequential stamping procedure by reshaping the matched tool components proved significantly more complicated. In fact, many problems surfaced, including the increased costs of making and maintaining the tool components with the bowed configurations, the dramatically experienced wear on such components with more frequent reshaping needed to maintain proper specifications, and the fact that the severe material removal of the tool components during reshaping significantly shortened the available service live, compared to conventional tool components. Further, different matched sets of tool components might be needed to make similar piece-parts, each specific to a desired degree of curvature or bow.
Efforts to bend or bow stamped flat piece-parts to some desired degree of curvature likewise have left much to be improved on, as individual handling of the piece-parts has proven to be labor intensive and costly. Moreover, direct press or straightening equipment contact on the opposite surfaces of the piece-parts might typically cause surface marring and/or leave noticeable crease lines thereon.